Re: [Xen-devel] [PATCH 14/27] xen/arm: traps: Improve logging for data/prefetch abort fault

[Andre Przywara <andre.przywara@xxxxxxx>]

Hi,

On 14/08/17 15:24, Julien Grall wrote:
> Walk the hypervisor page table for data/prefetch abort fault to help
> diagnostics error in the page tables.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
> ---
>  xen/arch/arm/traps.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
> index 819bdbc69e..dac4e54fa7 100644
> --- a/xen/arch/arm/traps.c
> +++ b/xen/arch/arm/traps.c
> @@ -2967,7 +2967,26 @@ asmlinkage void do_trap_hyp_sync(struct cpu_user_regs 
> *regs)
>          do_trap_brk(regs, hsr);
>          break;
>  #endif
> +    case HSR_EC_DATA_ABORT_CURR_EL:
> +    case HSR_EC_INSTR_ABORT_CURR_EL:
> +    {
> +        bool is_data = (hsr.ec == HSR_EC_DATA_ABORT_CURR_EL);
> +        const char *fault = (is_data) ? "Data Abort" : "Instruction Abort";
> +
> +        printk("%s Trap. Syndrome=%#x\n", fault, hsr.iss);
> +        /*
> +         * FAR may not be valid for a Synchronous External abort other
> +         * than translation table walk.
> +         */
> +        if ( hsr.xabt.fsc != FSC_SEA || !hsr.xabt.fnv )

This is quite hard to read. Would the DeMorgan'ed version be better?
           if ( hsr.xabt.fsc == FSC_SEA && hsr.xabt.fnv )
               printk ....
           else
               dump_hyp_walk ...

> +            dump_hyp_walk(get_hfar(is_data));
> +        else
> +            printk("Invalid FAR, don't walk the hypervisor tables\n");

Nit: "not walking" sounds less ambiguous.

> +        do_unexpected_trap(fault, regs);
>  
> +        break;
> +    }
>      default:
>          printk("Hypervisor Trap. HSR=0x%x EC=0x%x IL=%x 
> Syndrome=0x%"PRIx32"\n",
>                 hsr.bits, hsr.ec, hsr.len, hsr.iss);

Ignoring the nits above:
Reviewed-by: Andre Przywara <andre.przywara@xxxxxxx>

Cheers,
Andre.

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